I am hoping to use a carry on only for my next trip but can't for the life of me figure out how to stay within the 100 ml limit for liquids. Wondering how you all do it.
I am not what I would consider to be high maintenance but, at the bare minimum, need shampoo, hair gel, facial moisturizer with SPF and foundation. I would normally bring conditioner, mousse, hairspray, lotion, sunscreen and perfume but can live without those or get some of them there when I arrive. The idea of wasting precious vacation time hunting for the equivalent of a Walmart doesn't thrill me or seem reasonable/likely in many European cities..
At 50, I am fairly particular about which brands I use and they aren't the cheap ones so I can't imagine buying them when I arrive somewhere (and paying in euros or USD) only to have to throw most of it out for the return trip.

How do you all manage this?

I always do carry on only and have no issues meeting the liquids requirements.

"shampoo, hair gel, facial moisturizer with SPF and foundation". can all be decanted from larger bottles into travel sized vials/tube/bottles.

"I would normally bring conditioner, mousse, hairspray, lotion, sunscreen and perfume" Same with conditioner, and lotions. Hairsprays and mousse can be found in travel sized containers. (I don't use either hairspray or mousse but do take lots of other liquids so offsets those). Every perfume I' know about has tiny travel sized options. Sunscreen is the one thing I would wait and buy on arrival if you need a lot.

"The idea of wasting precious vacation time hunting for the equivalent of a Walmart doesn't thrill me or seem reasonable/likely in many European cities.."
Popping into the nearest Boots or Citypharma or Galeries Lafayette is easy and can be a fun part of any trip.

. . . and unless you'll die if you have to use a different brand of shampoo / conditioner . . . every hotel/B&B/rental flat I've stayed in 20+ years has provided them.

Perhaps you are a bit confused. The 100 ml limit applies to each container not the total amount you are allowed. In your carryon you can bring as many 100 ml (3.4 oz) bottles that will fit in a 1 Qt ziplock bag.

We don’t worry about packing shampoo or conditioner as, like janisj said, every hotel/resort provides this for you. You can easily pack several “travel size containers of whatever hairspray, etc. that you can’t live without in the qt. size bag. We almost always take only carryon when flying and learned long to take only essentials and most items are not “essential” as you can do without just about anything for the week or so you are on vacation.

like janisj said, every hotel/resort provides this for you.
Depends where you stay... not always true -lol!

How long is the trip? If you experiment in advance, I know I can get by with 2-3 oz. containers of my favorite shampoo, conditioner, etc. for a trip even up to one month. I buy body lotion, sunscreen, upon arrival. Skip the mousse, hair spray, perfume. I stay at budget hotels and apartments and they do not supply toiletries, beyond perhaps a bar of soap.

I check in a suitcase, that’s how I manage it. I can’t abide carryon, all that pushing & shoving & trying to find space for carry on. Even in business class I can’t be bothered with carryon. But I understand there are big challenges in the US with checked luggage which is why many have carryon. I also don’t want to spend vacation time doing laundry.

There is nothing superior about traveling checked or carry on. But in the current chaos at many European (especially at LHR , MAD and AMS) and some US airports, carry on is safer/more convenient. Just spent a week in London -- some quite dressy some casual. Everything from garden show to theatre to Tiffany exhibition - didn't wear the same outfit twice and the only 'laundry' needed was washing out undies and drying them on the towel rail. Probably spent less than 5 minutes doing laundry the entire week. My roll aboard weighs about 20 lbs totally packed and is easy to lift into the overhead (and I'm petite so the overheads are literally way 'over head'). Was through fast track immigration and customs and on the tube into London long before any luggage from the flight hit the carousel. I'd rather waste 5 mins doing a bit of hand washing to avoid waiting . . . and waiting . . . for checked luggage . . . and sometimes not getting it for 2 or 3 days.

Never did any any 'pushing or shoving' that I recall.

Thank you.

I feel ridiculous asking this, but where do you even get travel sized perfumes? Do you just go to The Bay or Shopper's Drug Mart and ask for samples? The ones I have used before are tiny and I think I got them when I bought the bigger version

I agree about it being fun (potentially) to source things in Europe. When my luggage was lost before, hunting around a strange little discount mall in Garmisch-Partenkirchen for underwear became a memorable part of our trip

I won't die, but my thin, curly hair will if I don't use my brand of shampoo. Just about the only time I take pictures with myself in them is when I travel, so it is important to me to look nice in them.

RoamsAround, thank you. I am very happy to realize that I misunderstood the rule.

I totally get this. It will be a challenge for me for sure, but between having had my luggage lost once and the nightmare that air travel has become feel like I have to try.

Just forget about perfume. I find it very annoying when people on a plane, bus, train, wear perfume. When you know you are going to be around a lot of people, just leave the perfume home. Some people have asthma and are sensitive to such things.
I also think it's rude to wear perfume in restaurants. I don't want the aroma of anyone's perfume to interfere with the taste of my food.

If you don't have samples of your favorite perfume(s) you can buy either a small refillable atomizer like one of these
Or use other very small travel bottles.

Or use a scented soap or body lotion (you don't have to pack the soap in the ziplock bag). I don't travel with perfume either. I normally don't wear makeup but if I think I will need it I bring just a lipstick sized tube of concealer and something like bare minerals which also has sun protection and doesn't need to go in the ziplock.

May US airports seem to let the odd chapstick or lipstick packed in a purse go through okay. Bigger issues in Heathrow apparently.

Lipstick/chapstick etc are allowed in the UK -- just like solid deodorant they can packed anywhere in handbag/personal item/rollaboard - no issues at all. They aren't considered liquids. (They were lumped in with liquids back in 2006 when the limitations were first implemented but that only lasted a couple of years). I travel through LHR several times a year. It is the liquid versions (Lip gloss in a tube or pot, roll on deodorant) that need to be the the ziplok baggie.

I do not bring shampoo, as always in hotels. I do bring tiny tube of conditioner, hairspray, deodorant small stick, 2 or 4 oz saline solution for contacts, and my makeup. Not a problem, but always check my 24" suitcase for overseas 2 wk+ trips. Most stores overseas now stock small travel sizes, and easy to get.

Ditto

One word: downsize

Take your favorite shampoo & conditioner & hair gel but only just barely enough for the length of your trip. High quality stuff is very concentrated. I can get by for two weeks with 1 oz. of each of those. Same with face lotion. Body lotion or sun screen I buy upon arrival. Things like lipstick, stick deodorant, eye pencil, do not count as against your 1qt bag liquid allowance. Skip the perfume. Or tuck in one small sample.

What perfume do you wear that does not come in 50ml bottles as well as the larger bottles?

I can buy small plastic screw-top jars and bottles, with or without atomiser sprays at “ Cheap Charlie/ Dollar” shops and sometimes in my local supermarket.

I can easily travel for a month with a couple of tiny jars of face goo and the decanted bottles of shampoo & conditioner. Like you, I like the hair stuff I like, but it’s concentrates and I have short hair so don’t need much.

I bring all my toiletries and they would fit in carryon within those rules. You are fairly high maintenance to me. There is no reason on earth you have to travel with perfume. You don't need foundation, for example. You really don't need perfume.

I travel with a small size bottle of shampoo (2-3 oz I guess) , facial moisturizer, hand cream, body lotion, and some hair product I use which isn't gel but would be the same size which is a leave-in conditioner. Plus a small tube of toothpaste, of course. That's 6 small things which easily fit in that size bag you are required to use oh, yeah, I usually have a smaller tube of sunscreen also if summer, so 7 things.

Facial moisturizer and hand cream, etc actually last a long time, I never even use up those sizes during a trip. I have dry hair so only wash it once a week, though.